Normally, according to a dye image producing method in which a silver halide color photosensitive material is used, after an image-like exposure is effected, an oxidized p-phenilenediamine type color developing agent is caused to react with a dye forming coupler, whereby a dye image is produced. In such method, a color reproduction technique based on a subtractive color process is usually applied so that dye images in cyan, magenta, and yellow are formed on corresponding photosensitive layers in complementary relation to the three colors of red, green, and blue respectively. Recently, in order to shorten the development time required in connection with the formation of such dye images, it has become a usual practice to employ high-temperature development techniques and reduce the number of processing stops required. In order that the development time may be shortened through high temperature development in particular, it is very important to increase the rate of development in the process of color developing. The rate of development in the process of color development is subject to the effects of two sources. One of the sources is the silver halide color photosensitive material used and the other is the color developing solution used.
With the former it has been found that the particle shape and size in and the composition of the photosensitive silver halide emulsion used, in particular, have considerable bearing on the rate of development, while with the latter it has been found that the rate of development is likely to be influenced by the conditions of the color developing solution and, more particularly, by the type of the development restrainer used, and that grains of a high silver chloride in particular exhibit a remarkably high development rate under specific conditions, for example, such that bromide ions conventionally used for color development are not contained in the color developing solution.
In a photosensitive material for use as a color paper, a blue-sensitive emulsion layer is normally present as the lowermost layer, and therefore the emulsion layer is required to contain silver halide grains which show high sensitivity and a high rate of development. As one type of such technique for increasing the rate of development there is known a method in which a combination of a silver halide and a low-bromide silver is used, as disclosed in Japanese Published Unexamined Patent Application No. 58-184142 and Japanese Published Examined Patent Application No. 56-18939. However, with such method, wherein the silver chloride content of the emulsion layer is increased, the difficulty is that the photosensitivity is inevitably lowered. Such difficulty is attributable to the fact that pure silver chloride absorbs almost no visible light by nature. As attempts directed toward overcoming this difficulty there have been known methods using a combination of such spectral sensitizing dyes as mentioned in Japanese Published Unexamined Patent Application Nos. 58-91444, 58-95339, and 58-107532, or of such spectral sensitizing dyes having different wave lengths as mentioned in Japanese Published Unexamined Patent Application Nos. 58-95340, 58-106538, and 58-107531. However, no mention is made in these publications as to changes in gradation due to the use of a high silver chloride in combination with such dyes. As such, these combinations have not been successful for use in a color photosensitive material, or more particularly for use in a color paper.
It has also been found that the use of a spectral sensitizing dye in the form of a cyanine dye having two benzothiazole rings in a molecule cna enhance spectral sensitization in the visible light range, and more particularly in the light range of 430 nm-480 nm, thereby providing sufficient sensitivity even where a high-purity silver chloride is used.
In this case, however, the difficulty is that if the high-purity silver chloride is used in combination with such spectral sensitizing dye, a downward change in gradation will take place where development is effected with a color developing solution using p-phenylenediamine of the type which is normally used for the purpose of development, it being thus unable to obtain satisfactory color reproduction. Another difficulty is that where a developing solution having little or no bromide content is used with a view to increasing the rate of development, far much greater deterioration in gradation will result.
Recently, in order to minimize possible pollution loads arising from the processing of silver-halide photosensitive materials, there has been a strong demand for elimination from any color developing solution of benzyl alcohol, a coupling improver. If such demand is considered in conjunction with aforesaid color developing solution having no bromide ion content, that is, if a color developing solution containing neither bromide nor benzylalcohol is used, it has been found, a photosensitive material using such spectral sensitizing dye and such high-purity silver chloride grains will not only show an excessively decreasing gradation, but also will excessively enhance reduction in maximum photodensity.